There are hydraulic systems which use a directional control valve to control flow to and from rod and head sides of an actuator. However, directional control valves can be quite expensive and may result in performance inefficiencies (e.g., energy/fuel inefficiencies). As a response to this issue, some hydraulic systems have been designed without a directional control valve and instead rely on a bi-directional variable displacement pump to direct flow between rod and head sides of the actuator.
In the context of hydraulic systems, flow continuity relates to the need of a hydraulic pump to experience continuity in the flow of hydraulic fluid therethrough. This requirement is implicated particularly in circuits that have been designed without a directional control valve and instead rely on a bi-directional variable displacement pump to direct flow between rod and head sides of an actuator. The unequal areas of the rod and head sides result in unequal flow volumes to and from the actuator, which, without proper accommodation, could interrupt flow continuity at the pump.